Funds are urgently needed to purchase a Finnigan SSQ-70 quadruple mass spectrometer to replace the University's only instrument, a Finnigan 4023 quadruple, which is now 10 years old and no longer fully serviceable. This request has been necessitated by a lack of reliability, excessive down time and untenable operating condition of the old instrument as well as the expanded needs of the investigators at the University. Some of the original subsystems of the Finnigan 4023 are obsolete and cannot be readily repaired since replacement parts and/or service are no longer available. In the context of a multiple-operator facility with very heavy user demand and a wider variety of samples for analysis, a new instrument will fulfill current needs for (1) additional features and capabilities, (2) a reliable instrument, 93) increased sensitivity, (4) faster analysis time, and (5) simplicity of use and maintenance for multiple users. The existing instrument has been successfully operated as a University wide resource since 1979 under the guidance of a User's Advisory Committee composed of representatives from all major departments including Biochemistry, Pharmacology, Molecular Genetics, Internal Medicine, Physiology and Pediatrics. As a unique University facility, this instrument is available to all faculty of the University of Texas Southwestern Medical Center. In addition, it has been used by investigators from other institutions of higher education in the Dallas area on a time available basis. A functioning, multi-task instrument is vital to current studies requiring characterization and quantitation of samples produced by (a) enzyme preparations and subcellular components, (b) vascular cells, (c) adrenal cells, (d) heart tissue, (e) whole organ and animal systems, (f) human subjects and (g) chemical synthesis. A wide carbohydrates, antibodies, polycyclic aromatics, prostaglandins, leukotrienes are related oxygenated fatty acid metabolites, diterpenes, stable isotope labeled standards, cyclitols, oligopeptides, drugs and other xenobiotics.